Steel wool consists of fine strands of steel which looks a bit like wool.
It can be used for cleaning, scouring and sanding.
I use it manly for cleaning pots. Same principal as a brillo pad but without the plastic packaging.
It can be bought from hardware shops and many of them sell it plastic free in either cardboard or paper packaging. However the trend is for increased plastic packaging so you might have to shop around!
The picture of the cardboard packaged steel wool is from the B&Q website so could look there.
More About Steel Wool
Steel wool comes in different thicknesses (grades).
The thicker the wool the more powerful the scouring / sanding.
I took the following from the Liberon Steel Wool website
Steel Wool is available in 7 grades from Ultra Fine 0000 through a range of Fine to Medium 00, 0, 1 and Medium to Coarse 2, 3 and 4.
Grade 0000 - use to cut back between coats of French Polishes, varnishes and oil finishes - use to clean and polish metals such as bronze, copper, chrome, stainless steel and aluminium - use to cut back between coats of varnish or paint - use with soapy water to clean and polish porcelain, marble and glass without marking Light cleaning and surface preparation
Grade 00, 0, 1 - use with Liberon Wax and Polish Remover to remove built-up wax polish, smoke and dirt on wood - use to clean, smooth and prepare wood or metal surfaces before re-polishing, waxing, varnishing or painting - use with a suitable solvent for light to medium cleaning of all metals Heavy cleaning and paint and varnish removal
Grade 2, 3, 4 - Use with Liberon Fine Wood Stripper to remove softened French Polishes, varnishes, lacquers and paints from wood and metal surfaces - use to remove rust
To avoid cuts never tear steel wool, cut to size with scissors or shears and always protect your hands with gloves when handling.
Always test products on a spare surface or inconspicuous area first.
If in doubt use a finer grade first.
You can find more pot scouring options here