along with; in accordance with
Describes doing something in accordance with or along a guideline, policy, or plan.
This pattern means 'along' or 'in accordance with' something like a rule, plan, or procedure. It is used when an action is taken following the direction or content of that thing. It is often used in business, school, or official contexts, and it is not used for physical directions like 'walk along the river' (that would be 沿いを歩く).
You can also use the form に沿った + noun to modify a noun, meaning 'that follows/in line with.' For example, 計画に沿った行動 means 'actions in line with the plan.' The pattern is slightly formal and more common in writing or official speech, but you will hear it in meetings and announcements too.