What is the full form of LSTM? What is its function?

LSTM is a recurrent neural network (RNN) architecture that **REMEMBERS** values over arbitrary intervals. LSTM is well-suited to classify, process and predict time series given time lags of unknown duration. Relative **insensitivity to gap length** gives an advantage to LSTM over alternative RNNs, hidden Markov models and other sequence learning methods.

ref: https://medium.com/@kangeugine/long-short-term-memory-lstm-concept-cb3283934359