To visit Israel you need a passport valid for at least six months from the date of entry. If you hold an Israeli passport, you will be required to present it upon arrival.
Many countries have a Visa Waiver Program with Israel, which allows their citizens to visit Israel without a pre-arranged visa. Citizens of Australia, Canada, the EU, and the USA do not need a visa for touristic stays up to 90 days. Citizens of other countries can check if they need a visa at www.mfa.gov.il/MFA/ConsularServices/Documents/VisaRequirements-Tourists.pdf
Because of diplomatic issues, you might not be able to travel to some Arab or predominantly Muslim countries if your passport shows an Israeli visa or stamp. To solve this problem, your visa will be stamped on a separate entry card when you arrive in Israel.
Remember to bring your passport with you on trips to Palestinian territories: it will probably be required at checkpoints and border crossings.