As you may have already seen, mathematics is a mixture of operations, signs, numbers, and symbols. The numbers are concrete values, constants that can be manipulated to form new values. Symbols (or variables) typically come in the form of letters. While we can still apply operations, they do not possess any concrete value unless we assign one or solve for them in context. This is known as algebra.
Below is a list of algebraic vocabulary you should familiarize yourself with.
We'll use the following expression throughout the table as a common reference point: ${x}^{2}+2x6x+3y+4$
Algebraic Term  Definition  Example 

Algebraic Expression 

$${x}^{2}+2x6x+3y+4$$ 
Term 

$$2x,{\textstyle \phantom{\rule{0.278em}{0ex}}}6x,{\textstyle \phantom{\rule{0.278em}{0ex}}}3y,{\textstyle \phantom{\rule{0.278em}{0ex}}}4$$ Notice that the sign is also associated with the term. $$2x,{\textstyle \phantom{\rule{0.278em}{0ex}}}6x$$
$$3y,{\textstyle \phantom{\rule{0.278em}{0ex}}}4,{\textstyle \phantom{\rule{0.278em}{0ex}}}2x,{\textstyle \phantom{\rule{0.278em}{0ex}}}{x}^{2}$$ 
Variable 

$$x,y$$ $y$ is a factor of $3y$ 
Contant 

$$4$$ 
Coefficient 

In $2x$, $2$ is the coefficient. $2$ is a factor of $2x$, $2$. 