TYL has 2 meanings
Tell you later
Hey, when are we meeting at Mike's?
TYL - he still hasn't gotten back to me.
|CUL||Call you later|
|BBL||Be back later|
|cul8r||See you later|
|LBF||Later, best friend|
|T2UL||Talk to you later|
|CFS||Care for a secret?|
|Spill the tea||Share the gossip|
Thank you, Lord
People who just received good news use TYL to mean "thank you, Lord." This acronym is akin to a "huzzah!" or a sigh of relief.
Someone who uses TYL to mean "thank you, Lord" is likely religiously-minded. So, you should keep that in mind when replying to their message. For example, you may not want to reply with YW.
TYL! I'm glad to hear everyone is home safely.
In text and chat messages, TYL most often means "tell you later." When someone sends you this acronym, it means they plan to provide the information you want at a later time.
People often use TYL when discussing sensitive or complicated topics, which are better explicated IRL. They may also use TYL when they can't currently answer your question, and need time to track down more information.
Other meanings of TYL
In some instances, TYL may instead mean "text you later." For example, SOs who frequently correspond over text may end their conversations with TYL, to let their partner know that they'll check in again later.