RNA-seq data usually provides a snapshot in time of the transcriptome of that which is being sequenced. Single-cell sequencing is possible, but less common than RNA-seq on a sample (containing many cells).
You are correct that RNA-seq provides one with knowledge of RNA sequences, like AUGGUCAUCAG and so on. However, one will not necessarily have information about all possible RNA sequences from a particular species. Performing RNA-seq on the same cell type of a species at two different time points, or two different cell types at the same time point, may result in different profiles for the RNA sequences you get back. It depends on which parts of the genome are being expressed by the cells in a sample at the time of RNA extraction.
The data one gets back from RNA sequencing depends on the technology and company used. Typically, RNA-seq involves using a reverse transcription step so that the sequence data you get back is actually reported as the cDNA version of your original mRNA transcripts. Usually one gets a (very large) file of sequencing 'reads'. One can either then 'assemble' these directly to form a snapshot of the transcriptome or one can map them to a known reference genome. One of the main benefits of RNA-seq is that we learn not just what the sequences of the RNA molecules are, but also their relative abundances within the sample. Knowledge of this can be particularly useful in testing or developing a large range of biological hypotheses.