Campaign Objective

The campaign objective is the goal you tell LINE to optimize toward, set once at the campaign level.

Your choice controls who LINE shows the ad to, which bidding options appear, and what counts as success. Reach optimizes for impressions, Website Conversions for on-site actions, Gain Friends for new followers. The system spends the budget hunting for the outcome you named.

Pick Website Conversions and LINE looks for people likely to buy; pick Reach and the same budget instead chases the widest cheap impression count, two very different deliveries from one creative.

Optimization follows the objective, not your intent. Choosing Reach because it looks cheap and then expecting sales is the classic error. LINE delivered exactly what you asked for, just not what you wanted.

The objective is the instruction; pick the one that matches what you are paid on.