Buffers have many applications. Some of these are
Maintenance of life
Most biochemical processes work within a relatively small pH range.
The body uses buffers solution to maintain a constant pH.
For example, blood contains a carbonate/bicarbonate buffer that keeps the pH close to 7.4.
Enzyme activity depends on pH, so the pH during an enzyme assay must stay constant.
Many shampoos use a citric acid/sodium citrate shampoo to maintain a slightly acidic "pH balance".
This counteracts the basicity of the detergents present in the shampoo.
In baby lotions.
Baby lotions are buffered to a pH of about 6.
This hinders the growth of bacteria within the diaper and helps prevent diaper rash.
In the brewing Industry
Buffer solutions are added before fermentation begins.
This prevents the solutions becoming too acidic and spoiling the product.
In the textile Industry.
Many dyeing processes use buffers to maintain the correct pH for various dyes.
In laundry detergents.
Many laundry detergents use buffers to prevent their natural ingredients from breaking down.