You probably get a better answer asking Chatgpt to summarize some points for you, I would say Google it but since you came in to the forum asking, then you probably are too lazy for that 
Good thought. He'll get some of the best answers if he goes the chatgpt route. Because his question is so wide and can be answered from different points depending. Since the OP wasn't specific then whatever answer he gets, he may have to provide a feedback to help us refine the response to what he's asking. I think I answered him properly already, and he hasn't come back so
Per OP, maybe he is pertaining to transactions? It would be fitting since bitcoin just reached a new ath and maybe he is curious what will happen if too many people use bitcoin all at once. In that case, the answer is just higher fees so your transaction gets prioritized.
More interesting to learn is ATH events have mostly to do with exchange movement. Not blockchain movement. This current ATH was a lot of people shorting on derivatives and forced to buy back contracts. That doesn't do anything on blockchain itself. Trader mania only eats up exchange resources