Why A digital mode hotspot is a very low power transceiver (usually a few milliwatts to tens of milliwatts) paired with a small computer such as a Raspberry Pi. Your handheld DMR, D-STAR, Fusion or P25 radio talks to the hotspot over the air on a simplex frequency, and the hotspot passes the digital stream to the internet to reach a reflector, talkgroup or repeater network. It is essentially a personal gateway that gives you network access where no local digital repeater is in range.
Watch out The FT8 choice is tempting because FT8 is also digital and internet-adjacent, but FT8 is a weak-signal HF mode decoded by software on your own computer, not relayed through a hotspot; RTTY and meteor scatter operating have nothing to do with hotspots either.
Hotspot = tiny personal gateway: handheld in, internet digital network out.