In a poem, a two-syllable unit of text that's pronounced with equal stress on both syllables is a spondee. Words like "childhood" and "woodchuck" are usually pronounced as spondees.
Like the iamb, the anapest, and the dactyl, a spondee is a metrical foot. Rather than structuring the meter of an entire poem, a spondee is more likely to show up as an irregular foot, altering the rhythm or adding interest to a line. If you read a poem out loud at a high volume, and you hear yourself placing equal emphasis on two syllables in a row, you might have found a spondee. Congratulations!