Confused re lines of resolution vs pixels

I'm looking into purchasing an HDTV-ready television. I know that HDTV is broadcast in either 1080i or 720p. Most (all?) DVD players send a 480p signal. How do these numbers relate to the number of lines of resolution of a set? For example, if a TV has 800 lines of resolution, is it capable of getting the best from 1080i? or does it need more lines of resolution? Also, the HDTV's I've seen do not accept the 720p signal, only 480i, 480p and 1080i. Can someone please tell me what is and what isn't important to know? Thanks.
From what I believe that these are completely two separate issues. Lines of resolution is a constant finite number defined by the broadcast television system. and pixels is a totally digital issue. It is no wonder that HDTVs with different digital formats will not accept other signals.
Ok; the scan rate ; the lines of resolution; and the pixels--ALL make up your picture. Don't worry to much,Few tvs have enough pixels( read;none) -- to resolve true Hi Def in its entirety. To make matters even more depressing; HBO, OTA (over the air) broadcasts aren't in full HD anyway. Projectors with 9in CRTs do resolve the full pixel count--somewhere near 2 million.