Allophones are phonetic variations - different pronunciations - of the same phoneme. Using a different allophone does not change meaning.
The /l/ sound is pronounced differently in ‘love' and in ‘wool'. These two words contain allophones of the phoneme /l/.
In the classroom
It is important to be aware of what allophones and phonemes exist in other languages, as these can cause problems when learning the sounds of English. For example, the /b/ and /v/ phonemes in English are only allophones in Spanish and Spanish learners often have difficulty recognizing the difference. Discrimination activities on minimal pairs of words, distinguished only by the phonemes concerned, can help with this.