You can enter a gene symbol (like BRCA1) or a transcript ID.
A transcript ID can either be a RefSeq ID (like NM_000014) or a UCSC Known Gene ID (like uc001lsx).
It is recommended to use gene symbols approved by the nomenclature committees for human (http://www.genenames.org) and mouse (http://www.informatics.jax.org/mgihome/nomen). You may also enter a gene alias (like RNF53) although it is not guaranteed that the lists of aliases are exhaustive.
The search is an exact one and is case insensitive. However, you may use an asterisk (*) as a wildcard on the right side of your search term. For example, "STAT*" will retrieve all hits for all STAT genes as STAT1, STAT2, STAT3, STAT4, STAT5A, STAT5B, and STAT6 but also for STATH, the gene for statherin.