Fleet tenders were non-combatant capital ships attached to fleet forces like the Imperial Navy and the New Republic Defense Force, designed to carry military cargoes along interstellar supply-lines to replenish front-line vessels.
Little is known of Imperial fleet tenders such as the Moff Weblin, but it is known that 300m Star Galleon cargo/escort frigates were used as support ships for Star Destroyers by Grand Admiral Thrawn, while the full variety of cargo vessels in an Imperial Force Support ranged from corvettes to massive Field Secured Container Vessels.
In the early years of the New Republic, a shortage of suitable vessels meant that combat warships like the Larkhess were stripped of their crews and put to hauling cargo, but subsequently, Hajen-class tenders were built as a standard component of the New Class Modernization Program were, using the same 375m hull as the Sacheen-class light escorts, and shared the same fast hyperdrive.
Hajen-class ships were heavily automated, with a crew of just six, plus a sizable complement of droids; Imperial vessels like Moff Weblin were probably significantly less automated than this: their crews included a captain, a chief engineer, and at least two duty watches.
In part, the increased prominence of Fleet tenders under the New Republic was due to a wider difference in capital ship design philosophy. The vessels used by the Imperial Navy were designed to be self-sufficient: Star Destroyers could go several years without resupply, and smaller cruisers could similarly operate unsupported for a year or more—up to two years in the case of a Dreadnaught Cruiser or an escort frigate. In contrast, none of the New Class designs were capable of more than a few months' operation before needing resupplied, and in practice, the New Republic's fleets were constantly being replenished with new supplies by a stream of Hajen-class ships traveling between their patrol areas and bases far to the rear.
This strategy, however, made New Republic military supply-lines vulnerable, and this may, in part, account for the reversion to older, more self-sufficient Imperial-style capital ship designs during and after the Yuuzhan Vong invasion.