A portable base station collapses the whole radio access network and a compact core into a single transportable unit. Where a fixed deployment spreads the radio unit, distributed unit, central unit and core across a site and a data centre, this puts them in one rugged case with its own antenna and power, so a working 5G cell exists wherever the case is opened.
It is defined by deployability. It runs on a hot-swap battery, solar or vehicle power, stands up in minutes with auto-configuration, and is built to a rugged, ingress- and temperature-rated envelope. The core is on board, so the cell can break out traffic locally — devices on site talk to each other and to local compute whether or not any backhaul exists.
Backhaul is optional, not assumed. With a satellite or NTN link it joins the wider network; without one it runs as a standalone island network, which is exactly what tactical, disaster-recovery and remote deployments need. This is the distinction from the private 5G network-in-a-box, which is a fixed enterprise install — same all-in-one idea, different form factor and use case.