Alpha Reader: Usually used after initial completion of a manuscript. Checks continuity, scene structure, plot holes, etc. Does not check spelling or grammar!
Beta Reader: Used after a manuscript is polished and ready to submit to agent/publisher. Checks grammar, flow, continuity, etc.
Don’t ask your friends. Don’t ask your loved ones. Don’t ask anyone that is near and dear to your heart. Not out of fear that your friendship will be ruined over a particularly harsh bit of criticism. That’s exactly the type of feedback you want! Straight and to the point. The reason I admonish writers to avoid asking loved ones to critique their manuscripts has nothing to do with my feelings that writers can’t take criticism; writers can definitely take criticism. Better yet, writers have to take criticism. The reason for my admonition is due to the idea that, generally speaking, our friends and family are reluctant to give honest, blunt feedback because they know how much our manuscript means to us, and they don’t want to crush our dreams. They are the least likely readers to tell you that your scene/chapter/book sucks. Unless you have another writer friend that is willing to alpha/beta read, then, by all means, ask away! Just don’t be surprised when your writer friend comes to you with their 200,000-word manuscript asking for a little quid pro quo. When you find those perfect alpha/beta readers, hang on to them! Never let them go, and treat them like gold. They will be the reason your manuscript goes from a fecal waste field to a lush literary garden.