Plotting in Mathematica

(* stuff that is surrounded by parenthesis-asterisks are ignored "comments" *)

ClearAll["Global`*"]; (* this line means "don't remember the values of any variables from other things that Mathematica has done recently. Instead, start over from scratch!" *)

f[x_]=amp*Sin [k x]; (* this is the basic function I want to plot *)
amp=2.2;k=2.6; xmin=0;xmax=10;  
(* semicolons mean " do this line but don't show me anything at this time"*)
(* Also, I can put multiple values on a single line when separated by semicolons *)

Plot[f[x],{x,xmin,xmax},PlotRange-> {-3,3}, PlotStyle-> {Red, Thin}] 
(*"Plotrange" sets the vertical scale. Otherwise, Mathematica would make some default choices *)
(* "PlotStyle" can include a whole host of other properties.. *)

Plot[f[x],{x,xmin,xmax},PlotRange-> {-3,3}, PlotStyle-> {Green, Thick,Dashed}]