Capacitance and voltage — the BOM fit check
This TAJT685K006RNJ is a 6.8 µF tantalum capacitor rated at 6.3 V DC, with ±10% tolerance.
ESR and temperature — what they mean on the board
The 5 Ohm ESR is on the higher side for a 6.8 µF tantalum — expect more ripple heating than a low-ESR polymer would give. For a decoupling cap on a digital rail, that ESR adds to the power-supply impedance; for an output filter cap, it limits the ripple current you can pass before the part cooks. The ESR climbs at cold temps, so at -55°C the effective filtering drops; budget for that if the circuit must hold regulation at low temperature.
Package and footprint — what fits the board
The footprint is 3.50 mm x 2.80 mm with a seated height of 1.20 mm — low-profile enough for tight stacked boards, but the molded body means no conformal coating issues on the side fill.
You can design it in without worrying about a last-time-buy window closing.