Definition of `*

Questions
1

I don know why having a hard time finding in the documentation what is the meaning of `* ? For example in

ClearAll ["`*"];

sometimes the aposthrophe is used alone. HELP.

2

All the symbols in the current context.

In[1]:= Context[]
Out[1]= Global`

In[2]:= q = 1;

In[3]:= r = 2;

In[4]:= q+r
Out[4]= 3

In[5]:= ClearAll["`*"]

In[6]:= q+r
Out[6]= q + r

See tutorial/Contexts in the (Help menu) Documentation Center or
http://reference.wolfram.com/mathematica/tutorial/Contexts.html online.