Built-In Functions and help:
There are lots of built-in functions in a MATLAB. The help command is used to find out what functions MATLAB has, and how to use them. For illustration, typing help at the prompt in the Command Window will represent a list of help topics that are the groups of related functions. This is a very big list; the most elementary help topics are in the starting.
For illustration, one of these is listed as matlab\elfun; it involves the elementary math functions. The other is the first help topics as matlab\ops that shows the operators which can be used in expressions.
To see the list of functions contained within aspecific help topic, type help followed by the name of the topic. For illustration,
>> help elfun
will represent a list of elementary math functions. It is a very big list, and is broken into trigonometric (for which the default is radians, but there are equivalent functions which rather than use the degrees), complex, exponential, and rounding and remainder functions.