This is the 15243rd most frequent Russian word.
портативной
Portable.
Here, 'портативной' is used as an adjective to describe the noun 'компьютер', indicating that the computer is portable.
Я купил новый портативной компьютер для работы.
I bought a new portable computer for work.
In this sentence, 'портативной' is an adjective that modifies 'устройство'. It describes the device's quality of being portable.
Устройство является портативной и удобным.
The device is portable and convenient.
Here, 'портативной' again functions as an adjective, modifying 'зарядное устройство', specifying its portability suitable for trips.