‘Also’ is an adverb in German which can be easily confused with ‘also’ in English.
'Also' usually means - so, therefore
Examples:
Ich arbeitete viel, also brauche ich jetzt Ruhe - I worked a lot, so now I need to rest.
Ich war voller Energie, also ging ich zum Fußballspielen - I was full of energy, so I went to play football.
die Ruhe - rest
die Energie - energy (Plural form - die Energien)