Plosives (also called 'pops') are bursts of air pressure created by certain consonant sounds — primarily 'P', 'B', 'T', 'D', 'K', and 'G'. When this air burst hits a microphone diaphragm directly, it produces an unpleasant low-frequency 'thump' or 'pop' that is difficult to remove in post-production.
The solution is a pop filter — a mesh screen positioned 2–3 inches in front of the microphone. The mesh disrupts the air burst before it reaches the diaphragm while remaining acoustically transparent for sound waves. Most pop filters use nylon mesh or perforated metal and cost $10–20. This is the cheapest and most effective upgrade for vocal recording.
Alternatively, singing or speaking slightly off-axis (at a 30–45 degree angle to the microphone instead of directly into it) dramatically reduces plosives without a pop filter. Many experienced vocalists develop this technique instinctively. Windshields (foam covers) reduce plosives moderately but are less effective than a dedicated pop filter.