Algorithm is a sequence of steps or statements which are unambiguous. The algorithm must terminate in finite number of steps. An algorthm is a procedure to find or calculate some thing. At each step, there must be exactly one way of doing that step (without confusion, at any time) ie., it is well defined.
For example: the following satisfies the above conditions.
1. Input a value for variable N
2. let reminder when N is divided by 2 be R
3 if R = 0 then print that "N is EVEN" and GO TO step 5
4 print that " N is ODD "