A "placeholder" is a temporary object or symbol used to hold a spot for something else to be added later. It helps to indicate where something should go without specifying what it is. Full definition
Only about a quarter of those sites contained any content at all, which leads the agency to believe they are serving as placeholders for future crowdfunding portals, perhaps readying to launch once the SEC implements its investor guidelines. (inc.com)
It treats its characters as placeholders for philosophical arguments and spends the majority of its running time trying to «solve» existential mysteries without adequately exploring them. (metacritic.com)
This is a Thursday, which is immediately suspicious, but it doesn't appear to be on any sort of placeholder date. (gamingtrend.com)