In the coming decades, the search for life outside our Solar System will be undertaken using astronomical observations of extrasolar terrestrial planets. To better inform our search, the NASA Astrobiology Institute\‘s Virtual Planetary Laboratory team uses a suite of computer models to explore the interaction between a terrestrial planet and its parent star. The resulting models allow us to simulate extrasolar terrestrial planetary environments and spectra, and to define and quantify likely signs of planetary habitability and life. This talk will discuss the VPL models and results to date, including the detectability of planetary habitability and potential signs of life from alternative biospheres.