Born in Moravia in 1856, Freud proved himself over the course of his career both an impressive psychologist (being the one to create the term psychoanalysis) and a controversial theorist, many of his theories being either called into question at the time or as of now completely disregarded as insane or completely baseless.
However, it is important to note that regardless of how recognised within the context of psychological analysis, he is still a relevant historical figure in how he managed to shape a great many of our current perceptions, manners of speech and overall ideals of typical behaviour when isolated from the opinions of more learned experts.
The theories he held which can be called into question but for the most part seem to hold water are those of he tripartite mind (originally only bipartite as he had only initially theorised on the existence of the Id and Ego), which dictated that the mind is separated into three parts: The Id, the Ego and the Super Ego. These three sections he theorised operated as follows:
The Id - This was believed to be the unconscious desires. These would be the innermost primal, violent, sexual predilections, the central part of a man's soul that can not be directly contacted through normal means and constantly hungering for more. Supposedly through hypnosis Freud could draw this part out to attempt to gain greater insight to the patient's mind. However, it supposedly can not be reasoned with and it must simply be put to a more efficient and creative use or suppressed in some manner, though the latter was highly advised against as the consequences could be disastrous.
The Ego - This is the concious and logical, reasonable section of the mind, designed to regulate between the Id, Super Ego and outside world and supposedly the weakest of the three sections because of this fact, constantly under attack from the demands of all three and attempting to find a reasonable middle-ground between them all. Freud suggested that through his techniques he could help strengthen the resolve of the Ego so as to prevent a mental breakdown through the Ego failing.
The Super Ego - Believed to only come into existence subsequent to a person's formative years when they have become aware of the outside world and society's specific ideals, feeding off of these influences and twisting them so that they become less necessary regulations and beliefs and more demanding, impossible requirements that the Super-Ego imposes on your mind. Typically this is characterised as a form of policeman within the mind, ordering everything rigidly.
This theory was not new, hailing back to the time of Plato. However, the exact manifestations and arguments put forth on the matter differ dramatically. Plato theorised that it was the Rational side of the soul which controlled the mind, acting as a charioteer controlling the horses of the Spirited and Appetitive sides. Freud however believed that ultimately the Ego was more holding on for dear life, attempting to reign in wild stallions which could only be calmed for a time before the chariot would break.
The issue with this theory is that there is no determinate way of defining the existence of the Id in such a precise and clear-cut manner. Theorising on its existence is all very well, but to attempt to pin it down as anything tangible as Freud was suggesting was possible through his techniques does not seem logically plausible.
That said, this theory has been the influence for a great many works, particularly outstanding being those of Dr Jekyll and Mr Hyde, in which the Ego and Id are physically represented in the titular characters and the Super-Ego in the investigators and L'age D'Or, in which the main male character appears to be the ultimate representation of everything which supposedly comprises the Id, being sexually ravenous and monstrously violent to all who are either perceived to or definitively do get in his way. It can be argued that the film is entirely devoid of a representation of the Ego, being purely of the extremes between the Id and Super Ego and the effects if the Ego were to completely deteriorate into nothingness.
However, at odds with his theory of the extremes being primarily in control was Wilhelm Reich, who believed in a more layered, less disparate soul, still in a tripartite form, but more inter-connected as opposed to being independent of each other; his belief was that on the surface everyone is reasonable and well-mannered, acting in a logical fashion; the second layer he believed to be the cruel, callous, selfish, irrational side of a human; however the third layer, at the very core, he believed all humans to be inherently good and decent, and that their innermost love superseded the violent nature.
In both cases these theories simultaneously have logic to them and could be laughed out of any medical council for being insane and nonsensical. The primary issue is finding a way to bridge the gap between what is logically definable and what is simply speculation on the composition of the psyche.
The theories of Freud's which do not really hold any water are theories such as penis envy, which had no logical explanation and seemed to simply be based in having had a little too much cocaine on a particular day and projecting his own acquired insecurities onto women. Furthermore his idea of the Oedipus Complex feels like a somewhat tacked on belief as it was suggested that it was a symptom typically only found in infants, whose perceptions of the world can not possibly extend past that of their parents and thus have no comprehension of any instinctual habits past personal, physical survival.
However, another theory of his which has wormed its way into society today and appears to hold a modicum of truth to it is the "Freudian Slip". This theory is that you may slip up on a word or sentence and reveal your true feelings or desires. For example, instead of saying "The moon is big tonight" you slip up and say "Your breasts are big tonight". However sometimes the slip can just be a slip, which coined the phrase "Sometimes a cigar is just a cigar".
Ultimately you must take from Freud's teachings what you personally feel ring true. Some may believe that the Oedipus Complex is correct and the tripartite soul is complete rubbish. It is all down to the reader's/listener's discretion.