Definition
Pseudorandom is a quality of either functions or sequences of numbers that are random but derived from a particular starting point and involve successive repetitions.
Understanding the term
Pseudorandom numbers are statistically random and selected by a computational process. Any pseudorandom sequence of numbers or a set of elements is supposed to have all of the properties of a random sequence except true randomness that follows probability distribution.
However, the origin of a pseudorandom sequence occurs using a deterministic algorithm. Pseudorandom sequence generators for numbers are prevalent in cryptography, but the other most common pseudorandom sequence for cryptos is PRF (pseudorandom function family).
Creating a pseudorandom sequence requires a specialized algorithm, as mentioned above. Such an algorithm would ensure that the generated sequence of numbers has the same properties as a randomly generated sequence of numbers.
What makes pseudo-randomness different from true randomness is that it relies on a mathematical algorithm for its generation. As random numbers are considered a principal tool for cryptographic applications, pseudorandom sequences of numbers are generated in a way that is indistinguishable from true random bits.
Takeaway
Pseudorandom numbers are secure for all sorts of cryptographic purposes as they are computed using a deterministic computer algorithm to be like true random numbers.