‘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)