‘Net zero emissions’ refers to achieving an overall balance...

‘Net zero emissions’ refers to achieving an overall balance between greenhouse gas emissions produced and greenhouse gas emissions taken out of the atmosphere.

Getting to net zero means we can still produce emissions, as long as they are offset by processes that reduce greenhouse gases already in the atmosphere.

An example would be replacing coal fired power stations with a gas fired power station, or a solar farm, of the same capacity. Here you'd have an overall reduction in greenhouse gas emissions.

The argument of gas being a transitional fuel is to allow the gradual transition from fossil fuels to renewables by 2050. Battery technology is in its infancy, so there's an expectation gas can facilitate this transition.