imperfect Брать.
Present: Беру, берёшь, берёт, берём, берёте, берут. Past: Брал, брала, брало.
Impetfect future form: буду брать, будешь брать etc....
Perfect aspect: Взять.
Future: Возьму, возьмёшь, возьмёт, возьмём, возьмёте, возьмут.
Past: Взял, взяла, взяло.
The two words aren't exactly the _same_ word in the forms of perfect/imperfect aspect.
There exist other imperfect aspect of 'взять' - 'взимать'. Взимаю, взимал etc..
брать and взять share exactly the same meaning in different aspects - so we consider them the same word, while 'взимать' is pretty rare word used sometimes for taxes, tridutes etc...
Etymology:
вз- or воз- < възъ. Means 'up'
-ьм-/-я- < -им-
the same root in "ИМеть", поднЯть, понИМать....
In Old Slavic syllable им transformed into nasal vowel before consonants or in the word finale.
That nasal vowel later transformed into я in Russian.
Before vowels it didn't changed.
Later и dropped in some forms.