What is liner probing , rehashing and clustering?

What is liner probing , rehashing and clustering?

1. When collision occurs that is when two records demand for the same location in the hash table, then the collision can be solved by placing second record linearly down whenever the empty location is found. 
2. Hashing is an effective way to reduce the number of comparisons. Actually, hashing deals with the idea of proving the direct address of the record where the record is likely to store. 
3. Data clustering is a common technique for statistical data analysis, which is used in many fields, including machine learning, data mining, pattern recognition, image analysis and bioinformatic.