The alto in a choir will sing the lowest notes of the song available while the tenor will sing the highest notes for the male voice. For females, those who would sing the little notes are also called altos, but those who would sing the top notes are called sopranos. There are a lot of women who can usually sing songs that are sung initially by men if they are in tenor. The voices of females are generally higher as compared to men.
Not all females will have the voice range to sing songs that are sung by male singers. This is also the same with male singers. They can sing alto songs better as compared to soprano songs because of their vocal capacities and capabilities.