High-lift blades, a.k.a. standard blades or two-in-one blades, are the most commonly used blades for push and riding lawn mowers. Their "high-lift" design allows for greater airflow, enabling cleaner cutting and faster discharging of the grass clippings back to the lawn or into a bag. Note that high-lift blades are not an option if your lawn mower exclusively mulches or if you've installed a mulching kit on it.
Mulching blades, also known as all-purpose blades or 3-in-1 blades, are designed for push or riding lawn mowers that mulch clippings. Mulching blades cut the grass and then chop the clippings into finer pieces. This mulching enables faster grass decomposition so your lawn will reap the benefits of the nutrients sooner.