wht does 'at most one head or at most one tail' means and ' at least one head but at most one tail or at least one head but at most two heads' means...plz..ans.fast

suppose we are tossing a coin 5 times.
at most one head means either we get 1 time head and 4 times tail or we get 5 times tails only.
at most one head is either one head or no head.
at most one tail means either we get 1 time tail out of n times or we get no tail i.e. all are heads.
at least one head but at most one tail: 
if we are tossing a coin 5 times , at most one tail i.e. tail occurs either 1 time or it does not occur
i.e. out of 5 times either 4 times head and 1 time tail or head occurs all the 5 times.

hope this helps you