Plugin Help MyCommand - Variables

I didn't find anything useful anywhere about how custom variables work.

I don't understand how these variables would be made and how they would be displayed properly, and I really don't see how others learned how this works. Is there some tutorial I missed, or is this just all programming?

What I would like as a sidebar:

NexCraft
Player Stats:
Health: <>
Food: <>
Money: $<> (Essentials Economy)
Tokens: <> (Scoreboard Objective)
Credits: <> (Scoreboard Objective)
Kills: <> (Scoreboard Objective)
Coordinates:
<xyz>

Current Sidebar:
Player Stats:
Health: <>
Food: <>
Coordinates:
<xyz>

<> representing whatever value is there