Accepted Friday Jul 17, 2009
About 120 baryons and baryon resonances are known, from the abundant nucleon with u and d light-quark constituents up to the Xb-=(bsd) which contains one quark of each generation and to the recently discovered Wb-=(bss). In spite of this impressively large number of states, the underlying mechanisms leading to the excitation spectrum are not yet understood. Heavy-quark baryons suffer from a lack of known spin-parities. In the light-quark sector, quark-model calculations have met with considerable success in explaining the low-mass excitations spectrum but some important aspects like the mass degeneracy of positive-parity and negative-parity baryon excitations remain unclear. At high masses, above 1.8 GeV, quark models predict a very high density of resonances per mass interval which is not yet observed. In this review, issues are identified discriminating between different views of the resonance spectrum; prospects are discussed how open questions in baryon spectroscopy may find answers from photo- and electro-production experiments which are presently carried out in various laboratories. PACS: 12.39.-x; 13.60.-r; 13.75.-n; 14.20.-c