Structure Functions and Extraction of PDFs at HERA
  Results from the HERA experiments, H1 and ZEUS, on $e^\pm p$ deep inelastic scattering (DIS) provide an important contribution to the knowledge of the proton structure and QCD. The data were collected in the years 1994-2000 (HERA I) and 2003-2006 (HERA II) in the center-of-mass energy of $\sqrt{s} = 300$ GeV in 1994-1997 and 319 GeV from 1998. During the HERA II period, the lepton beams were longitudinally polarised. The most recent results on neutral current (NC) and charge current (CC) DIS cross sections from HERA II data are presented. Results on Parton Density Functions (PDFs) and the strong coupling $\alpha_s$ extracted from HERA I data are discussed. Accounting for the correlation of electroweak parameters with PDFs, a combined electroweak and QCD analysis is performed for the first time at HERA. 
N. Raicevic (the H1 and ZEUS Collaborations)