What does "low profile" stand for, connected to hardware?

When it comes to hardware I often read something like "Apple Mac computers, and other lower profile ...." For me it sounds like a better word for low end segment hardware but I am not sure about it. Google didn't help me well to answer this question. Is there something more connected to it? I need it to fully understand some articles. Term is used here for example: HBA H240

Storage controller - plug-in card - low profile

You have a few PCIe form factors:

You have different card and/or bracket heights:

FH - Full-height
HH - Half-height

And different card lengths:

FL - Full-length
HL - Half-lenth

"Low-profile" is synonymous with half-height, half-length (HHHL).

An HBA like the HP H240 is a half-length card that comes with full-height and half-height brackets, and can fit into either type of server slot. If using with a Server like an HP DL360p Gen8, this give you options on card placement.

In the linked example, it is a description of the interface card's "form factor" -- it's physical properties of size and shape. It's about half the height of a regular PCI-E card.

In a general sense "low profile" usually means roughly "thin" or to a lesser extent "small".

In the specific case of PCI and similar cards "low profile" means that the card is small enough to fit vertically in a 2U rackmount case or a desktop case of similar thickness.

Note that low profile slots require a different bracket (the metal piece that surronds the external connectors and joins card to case) from standard slots. A card with a low profile bracket won't fit in a standard slot. A card with a standard bracket can be inserted in a low profile slot but you won't be able to screw it in place or put the lid back on the case. Many low profile cards come with a pair of interchangable brackets to allow fitting in either standard or low profile slots but not all do.