When my oldest son turned 15 months he started showing interest in the potty. I was excited and thought that it meant he would be potty trained early. He was able to use the potty on command and was excited to use it. We put child sized potties in every bathroom and planned the end of our diaper days. We were very surprised when he was 3 1/2 and still not completely potty trained. I had many people tell me that he should have been potty trained by the time he was 2 or by the time he was 3. The simple fact was, he knew how to do it but he was not ready. When he was ready to potty train completely it went very quickly.
You can expose your toddler to the potty but do not pressure them. They will potty train when they are ready and not a minute sooner.