Gaby, algebra at any level kind of boils down to solving equations to find out the value of the variables. But that can take many forms at the 7th grade level.
Some equations just require isolating the variable:
subtract 5 from each side so x is by itself
But, other equations have exponents and you have to learn and remember rules for different situations. There are also rules for dealing with functions and line equations and graphing them, not to mention inequalities and word problems. It really takes a full length class to go over all of that so maybe you could ask questions as you go.