We live in a world in which people make statements about all sorts of things. The critical thinker wants to know which of these she should believe and which she should not. So she frequently challenges these statements. To accept the challenge is to produce an argument. When a person supports a belief with a reason, we call the supported belief the conclusion. We call the reason or reasons premises and we call the whole thing, the premises and the conclusion taken together, an argument.
Arguments have exactly one conclusion but have one, two or more premises. If a person provides reasons for two or more of their beliefs we consider each one the conclusion of a distinct argument.
English is a very difficult language to master, because compared to other languages it has a very large vocabulary and it has many irregularities in spelling and grammar.
The statement in brown is the conclusion. The two statements in blue are premises.
When we talk about reasons or premises that support conclusions what we mean are reasons to believe that the statement is true. Sometimes when people are asked for their reasons instead they will tell you something about their personal history which explains why they believe it. For example, when challenged they will say "I was brought up to think that way." or "That's what I've always believed," or "I guess I'm just a pessimist." Such an answer fails to offer the kind of reason a critical thinker is looking for. The critical thinker is not looking for a psychological or sociological explanation of why a given person believes something. The critical thinker is looking for an objective reason why any rational person would believe that the statement was really true.