In the example you give, there's actually no difference in meaning at all. Gerunds (verbs ending in "ing") and infinitives (to swim, to run, to walk, etc.) can both be used in that situation.

This is how I explain it: "To swim" is the action as a concept. It is something you look towards. "Swimming" is a reality. Gerund, remember? :) It already exists, and is an actual habit. So: "I like to swim" = I like it whenever I can do it. I probably don't have the chance to do it as often as I'd like. "I like swimming" = I already do this, and I do it often. I enjoy it.

I think "like to do st" means U do it becoz' it brings benefits for U and U know it. In contrast, "like doing st" means U love it and it's your favourite thing, U just do it coz' u want to. That's all :D

Some people feel that there is a slight difference: 1. I like TO SWIM is an unemotional, objective statement of fact. 2. I like SWIMMING seems more emotional and direct. Compare: It was nice TO SEE you again. Goodbye now. It was great SEEING you again. How about getting together for lunch one day?

I like swimming means your hobbies and the free time activity you are talking about. I like to swim we use with specific time you go to swim. I like to swim in the morning. I like to swim in the ocean in my next summer vacation.