When a current passes through a component, the charges do work against the resistance of the component. This work transfers energy from the electrical circuit to thermal energy in the component.
The component becomes hotter than its surroundings, so it transfers thermal energy to the surroundings by heating. We say the energy is dissipated, which means it is spread out into the surroundings and is not useful.
In a heater this is the useful effect. In a computer, a wire or a phone charger it is wasted energy. The higher the resistance, the more electrical energy is dissipated for the same current. Energy is never lost: it is conserved, but it ends up stored in the surroundings as thermal energy.