One of the basic skills of a technical writer is the ability to choose meaningful headings, captions, and titles. So, it's quite important to define the meaning of some words and phrases in order to be able to use them effectively. There are a variety of terms that are widely used for naming user documents, such as "user manual", "user guide", "reference guide", "instructions" etc.
Some people claim that the terms "guide" and "manual" are synonyms, so they use them interchangeably. Others, in turn, are sure that there is a significant difference between these words. Both explanations of the terms show us such types of documents as explaining materials containing detailed instructions, often step-by-step, as well as associated images (in a software industry screenshots of program's interface). So, to see a real difference let's refer to a dictionary and make the following conclusions:
However, in a modern IT world, technical writers don't always take those things into account and call the instructional documents according to some other criteria. Funny to mention is that today the word "manual" is associated with something old-fashioned and boring, so end-users are less likely to read such documents. On the other hand, the term "guide" is considered to be "in fashion" nowadays. Considering a guide as something short and up to a point, there is the opinion that creation of user guides is faster and end-users perceive them more positively. With this in mind, technical writers prefer guides to manuals. Indeed, such big companies as Microsoft, Apple, IBM tend to name their pieces of documentation "user guides", or sometimes "user's guides" regardless of the fact that these documents have all the characteristics of manuals.
There is one even more convincing statement explaining us that the "guide" refers to the software industry describing computer tasks, while the term "manual" serves for explaining hardware-related tasks.
Nowadays guides are easily created with the help of specific software documentation tools. To conclude, a term "user guide" is more often perceived as something useful and a "manual" is believed to be something boring and useless. Even though this tendency is not relevant in all situations and probably will not make difference in the world, yet it is essential to clearly understand what each type of technical document means.