Must Read: A very comprehensive reading on GIS
What I can do in GIS ?
a. Use ArcMap to edit/analyze geospatial data, to create ArcSDE table schemas.
b.Install the whole ESRI ArcGIS products in Windows/Linux OS, including Server, DB (SDE), and Desktop tools.
d.ArcSDE Java application development.
e.ArcSDE C#/.NET application development.
f.ArcGIS Server/DB Performance Tuning.
g.Cross GIS development from Google Maps, Google Earth, ESRI, to GeoServer/OpenLayers, and Leaflet.
h.Design and implement GIS solutions.