It may describe the some of the interesting facts that may go along with this sequence. This might include why it was sequenced, how it relates to other sequences in the database, some unusual features of the sequence, etc. Finally the sequence follows in lower case, in groups of 10 and with the number of the first nucleotide given on the left. The above example entry is a particularly short sequence. This is not the norm for NCBI entries.
Most entries contain a longer sequence as shown in the example below.
Nor is this the longest entry or even a particularly long entry by any means. There are many entries over 35,000 nucleotides in length. There are presently strong efforts to completely sequence the plant Arabidopsis thaliana , the nematode C. elegans , the fruit fly Drosophila, mouse and the human genome. For more information about NCBI go to their web site.