General question about 'for' loops

#1

i have seen different types of for loops
like –
for(;i!=n;i++)
for(i=0,j=0;condition;i++,j++)
can u tell their meaning and how to use them

#2

@sktg99
It works similarly:
for the first one, i is initialized somewhere outside the loop.
for the second case, it also works similarly both i and j increments together. when the loops loop will end will depend on the conditional statement.