http://www.musictheory.halifax.ns.ca/13ts.html
That should answer most of your questions. In regards to bpm, many times it is a matter of translating the Italian descriptions into the bpm- here's just a bit of info on that:
Basic tempo markings
From fastest to slowest, the common tempo markings are:
* Prestissimo 200 - 208
* Vivacissimo
* Allegrissimo
* Presto 168 - 200
* Vivo
* Vivace 140
* Allegro 120 - 168
* Allegretto
* Moderato 108 - 120
* Andantino
* Andante 76 - 108
* Adagietto
* Larghetto 60 - 66
* Lento
* Adagio 66 - 76
* Largo 40 - 60
* Lentissimo
* Adagissimo
* Larghissimo
All of these markings are based on a few root words such as 'allegro', 'largo', 'adagio', 'vivace', 'presto' 'andante' and 'lento'. By adding the -issimo ending the word is amplified, by adding the -ino ending the word is diminished, and by adding the -etto ending the word is endeared.
Common Qualifiers
* assai - very, as in Allegro assai (but also understood by some as "enough")
* con brio - with vigor
* con moto - with motion
* non troppo - not too much, e.g. Allegro non troppo (or Allegro ma non troppo) means "Fast, but not too much."
* non tanto - not so much
* molto - very, as in Molto Allegro or "Adagio Molto"
* poco - slightly, as in Poco Adagio
* più - more, as in Più Allegro; used as a relative indication when the tempo changes
* meno - less, as in Meno Presto
* In addition to the common "Allegretto," composers freely apply Italian diminutive and superlative suffixes to various tempo indications: Andantino, Larghetto, Adagietto, Larghissimo.
Mood markings with a tempo connotation
Some markings that primarily mark a mood (or character) also have a tempo connotation:
* Vivace - lively (which generally indicates a rather fast movement)
* Maestoso - majestic or stately (which generally indicates a solemn, slow movement)
* Sostenuto - Sustained, sometimes with a slackening of tempo.
If you are playing songs that you are already familiar with, especially pop/rock songs and most folk songs, this is overkill. 90+% are written in 4/4 time (4 beats to the measure). If you are already familiar with the song, you'll know the tempo. When working on a new song with tricky areas, what you want to do is start working on it slowly, perhaps as much as 50% of the tempo of the song. Work your way up to the actual playing tempo as you get better in those passages that give you trouble.
Hope this has helped at least a little bit. THere's a ton of information on the net for you on both of those subjects.