Basic stranded wire, "lamp cord", this is the most common wire.

Advantages:

1. Flexibility.

Disadvantages:

1. High relative self inductance.

2. Very prone to corrosion.

3. Low ring point.

4. Does not cancel its own ring.

5. Resonant and gritty sounding.

Not generally used or sold in high-end, it usually comes free with mass market speakers etc.

Check out the comparison between Cardas entry level cable, Crosslink, and 12 awg. Parallel Twin with clear jacket.

Solid Round
Bare Stranded Wire
Multi-Gauge Stranded Wire
Litz Wire
Clear Tubular Litz
Parallel Multi Solid Core
Constant 'Q' Stranding (Golden Section)
Matched Propagation
Conclusion