A catalyst is like a helper that makes things happen faster. Imagine you're trying to build a tower out of blocks, but it's taking you a really long time to stack them up one by one. Now imagine someone comes along and gives you a tool that helps you stack the blocks much more quickly! That tool is acting as a catalyst - it's making it easier for you to do something that would normally take longer.
In science, a catalyst is a substance that helps chemical reactions happen faster. Just like the tool for stacking blocks, a catalyst helps different chemicals react with each other more easily and quickly than they normally would. This can happen in all sorts of ways, like changing the shape of the chemicals, attracting them to one another, or guiding them through a process that helps them react more efficiently.
Using a catalyst can be really helpful in lots of different applications, from making new medicines to producing cleaner energy. Scientists study catalysts to find out which ones work best for different reactions, and they try to figure out how to make them even more effective. Overall, catalysts are like little helpers that make chemical reactions more efficient and powerful!