Final answer:
Plasmids are small, circular DNA molecules found in bacteria that can carry genes for advantageous traits. They can be transferred between bacteria through horizontal gene transfer.
Step-by-step explanation:
Plasmids are extra-chromosomal genetic elements found in bacteria that are small, circular, double-stranded DNA molecules. They can carry genes that code for advantageous traits like antibiotic resistance or the production of antibiotics. Plasmids can be transferred between bacteria through a process called horizontal gene transfer, which allows for the spread of beneficial genes.