This (m) acest acesta ăsta This (f) această aceasta asta These (m pl) acești aceștia ăștia These (f/n pl) aceste acestea astea That (m) acel acela ăla That (f) aceea acea aia Those (f/n pl.) acele acelea alea Yes, you are absolutely correct, acest băiat/ băiatul acesta. You also can use “acesta” to (or aceasta, acestia, etc) alone, meaning “this one” (or these), but never use “acest” alone, as it is an adjective and must be followed by a noun. Great job, keep it up!