When you select play on the media, does that media play, or some other bullshit get inserted first? Call it what you want, if it's serving me content I didn't

When you select play on the media, does that media play, or some other bullshit get inserted first? Call it what you want, if it's serving me content I didn't ask for, I'm not happy about it, especially if I'm paying extra for them to not do that explicit thing.