What are they ?
What are they used for
Neutralising acidic soils
Making chemicals that bind natural dyes to cloth
And many more things.
There are a huge number of reactions that you can perform with alkalis and other substances.
Alkaline hydroxide + acid → salt + water
Alkaline carbonate + acid → salt + water + carbon dioxide
Also interestingly alkali's can conduct electricity due to the presence of mobile ions.