Read info in htop

1. How to install htop:

sudo apt install htop

2. Info in htop:

    1) CPU usage:

        Number: CPU thread ID (1 CPU core = 2 CPU thread)

        Progress bar:

            blue: the percentage of CPU for low priority threads

            green: the percentage of CPU for user threads

            red: the percentage of CPU for kernel threads

            

    2) Memory & Swap:

        green: Used memory

        blue: Buffers

        yellow: Cache

* When RAM is full, it will use swap memory. Swap memory is much slower than RAM.

* Swap: By using a swap file, the computer can use more memory than is physically installed. In other words, it can run more programs than it could run with just the limited resources of the installed RAM. Swap files are not stored in physical RAM, which is why they are a type of virtual memory.