What is a chain?
Chains are a way to order the resolution of multiple card effects.

How do I know in what order the chains go?
After you and/or your opponent are done chaining eachothers effects, the order goes from Last Chain to First Chain

When can i start a Chain?
A Chain can be started anytime (DP->M1->BP->M2->EP)

*Starting a chain link at the wrong time*
If you are the turn Player and you set a trap after you have went into ur EP and end your turn, and your opponent activated Mystical Space Typhoon on the field from their last turn they set it. You can't activate that set trap card and start a chain, yes it will be destroyed and it could've helped you.

Example: You are running an exodia deck and you already have 4 pieces in your hand and you have no monsters on field, 1 card in deck, and only that one trap you set this turn. You cannot chain link that, lets say "jar of greed,"
trap card to MST do to the fact that your actual turn hasn't ended.

Anymore questions on "Chain Linking," you can get with me and discuss with me about it. Thank you