One reason for the power of C is its wide range of useful operators. An operator is a function which is applied to values to give a result. You should be familiar with operators such as +, -, /.
Arithmetic operators are the most common. Other operators are used for comparison of values, combination of logical states, and manipulation of individual binary digits. The binary operators are rather low level for so are not covered here.
Operators and values are combined to form expressions. The values produced by these expressions can be stored in variables, or used as a part of even larger expressions.