If you make a straight advance, you are going straight ahead.

直進 is a slightly formal-sounding word for direct forward motion. You'll often hear it in regard to the motion of vehicles, like when your GPS tells you to go straight at a light or an announcement on the train tells you the train will be going straight at the next junction.

This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.