This Is just a very basic lesson(Just doing this for zane mainly my next lesson will be wayyy better) on chain links. However basic this concept may seem it is a fundamental part of the game which many newcomers do not understand how it works.
Any way lets just dive into it.
What is a chain??
A chain is when you activate any effect and your opponent responds with an effect. Theoretically a chain can go on forever as you can respond to your opponents responses and they can respond to yours.
How do I start a chain??
A chain is started whenever a player activates an effect. During this grace period their opponent has time to respond with an effect. Its also important to remeber one can chain cards in response to their own cards.
Whats an Example of using chains beneficially?
For example in ritual beast they're are two cards. Ritual Beast ambush and ritual beast steeds. Steeds destroys monsters on the field up to the number of face up ritual beast monsters you control. Ambush summons 2 banished ritual beast monsters. You would want to activate steeds first and ambush second in order to get full destruction effects.
How do chains resolve?
Chains resolve backwards I.e. If you effect veiler dragunity dux(Y is he like castor konami!!!!!!) veiler would activate first negating dux's effect and then dux would attempt to activate its effect being negated.