The pits are known to be part of the fruit that will be in charge of protecting the seed. The only time when the seed will not be protected anymore is when the seed is ready to be put out. The seed is known to be the ovule. This will contain the embryo of the plant.
This explains why a lot of plants can only grow when you plant the seeds on the soil, although there are some plants that can grow without the seeds. Another difference between the two is the number of pits and seeds that are available in one fruit. Fruits will only have one pit, but the number of seeds that are available in one fruit may vary. For example, a banana will have more than one seed, but a rambutan will have just one per fruit.
Seeds and pits are not the same, although both are most times found together in a fruit. A seed is a fertilized ovule encased in fruit and starts germinating when it falls into the right environment and might end up growing into a mature plant. Seeds are usually found in the fruits, but a part of the fruits which covers and protects the seed before it starts growing. Some fruits have pits which can be very hard, and also, some of these pits are eatable.
There can be a lot of seeds in fruit or inside a pit, but just a pit is most times seen in fruits. While seeds are present virtually inside every fruit, on the other hand, pits cannot be found inside some fruits. For instance, pits are not present in some fruits like mango, while pits are present in fruits like cherry, peaches, plums, etc.