LSTM is a neural network which learns for an input x an output y. In additional to CNNs or MLPs it considers a hiddenstate h (which is influenced by prvious inputs) when your next input x is feed into the network.
Augmenting the feature Space is a technique which you do previous training your LSTM (to augment your data set in order to generatre more data and let the LSTM better generalize to new data). In the field of image recognition you can rotate your images by 40 degree to generate a new one. This process is known as data augmentation. Such methods also appliable to time series.
In summary: first, you start with augmenting your input feature space in order to improve prediction accuracy and then training your LSTM with the augmeneted training data set.