Chemists use a math formula called a rate law for every reaction. This law shows how fast the chemicals will turn into products. The specific rate constant is always written as a lowercase k.
It acts as a multiplier in that rate law equation. A large k means the reaction happens very quickly. A tiny k means the reaction moves at a slow crawl.
The word specific means this number is unique to one exact reaction. You cannot use the k from one reaction for a different reaction. Students often confuse the rate constant with the actual reaction rate.
The actual rate changes constantly as the chemicals get used up. The specific rate constant never changes based on chemical amounts. However, it changes drastically if you change the temperature.
Heating up the beaker makes the molecules crash together much harder. This extra heat energy makes the specific rate constant much bigger. A Swedish chemist named Svante Arrhenius figured out the math for this temperature change.