Picture an upright ruler with the ground at the bottom and the sky at the top. Low-level means the thing sits near the bottom of that ruler. What the ruler measures changes with the situation: height above the ground, rank inside a company, how strong a feeling is, or how close a piece of code sits to the machine. Going down the ruler does not make something worse. It makes it lower, smaller, milder, or closer to the basic parts.
From the word’s history
The word is simply low + level. Level can mean a height, a layer, a rank, or a point on a scale, and that is why one word covers flying low, junior staff, mild pain and machine-near code.
這個字就是 low 加 level。level 可以是高度，可以是一層，可以是位階，也可以是刻度上的一個點。正因為 level 這麼廣，同一個 low-level 才同時蓋得住低飛、基層、輕微，還有貼近機器的那一層。
Wiktionary entry for low-level (kaikki:3f6f69a190036ae4:1225425639:5314): "From low + level."
登入就可以看每一支怎麼連回核心畫面。