In my opinion

Functions which you have studied previously is the definion of functions and some other elementary things related to functions.

Now at Grade 11 you will study various types of functions like linear functions, quadratic functions, tignometric functions, algebraic functions, inverse trignometri functions and many more. Actually the underlying definition will be the same as you studied previously but the area and sense will become broad. Also you will study here how to tilize these functions in your daily life e.g. in banking and finance sector. As a function can be studied with the help of graphs. Many conclusions can be drawn by looking at the graph of a function. So you will also study here how to draw the graph of a particular fuction. And many more things you will enjoy by studying functions in detail here.