在Java或任何其他编程语言中将数据存入内存是什么意思？

I am a novice programmer and I recently started learning Algorithm and DS. I often see in tutorials and books the mention of the term "take the data into memory" like in sorting, Information Retrieval. Although I understand the process of storing data into an array or a HashMap (in case of IR) but I dont really understand what role memory plays in it?I am a novice programmer and I recently started