SnailisacommonnameappliedtomostofthemembersofthemolluscanclassGastropodathathavecoiledshellsintheadultstage.Whenthewordisusedinitsmostgeneralsense,itincludesseasnails,landsnailsandfreshwatersnails.Thewordsnailwithoutanyqualifierishowevermoreoftenappliedtolandsnailsthantothosefromtheseaorfreshwater.Snail-likeanimalsthatnaturallylackashell,orhaveonlyaninternalshell,areoftencalledslugs,andlandspeciesthathaveonlyaverysmallshell(thattheycannotretractinto)arecalledsemislugs.SnailsthatrespireusingalungbelongtothegroupPulmonata,whilethosewithgillsformaparaphyleticgroup;inotherwords,snailswithgillsaredividedintoanumberoftaxonomicgroupsthatarenotverycloselyrelated.Snailswithlungsandwithgillshavediversifiedwidelyenoughovergeologicaltimethatafewspecieswithgillscanbefoundonland,numerousspecieswithalungcanbefoundinfreshwater,andafewspecieswithalungcanbefoundinthesea. 　　Snailscanbefoundinaverywiderangeofenvironmentsincludingditches,deserts,andtheabyssaldepthsofthesea.Althoughmanypeoplearefamiliarwithterrestrialsnails,landsnailsareintheminority.Marinesnailsconstitutethemajorityofsnailspecies,andhavemuchgreaterdiversityandagreaterbiomass.Numerouskindsofsnailcanalsobefoundinfreshwaters.Mostsnailshavethousandsofmicroscopictooth-likestructureslocatedonaribbon-liketonguecalledaradula.Theradulaworkslikeafile,rippingthefoodintosmallpieces.Manysnailsareherbivorous,eatingplantsorraspingalgaefromsurfaceswiththeradula,thoughafewlandspeciesandmanymarinespeciesareomnivoresorpredatorycarnivores. 　　Snailsprovideaneasilyharvestedsourceofproteintomanypeoplearoundtheworld.Landsnails,freshwatersnailsandseasnailsarealleateninanumberofcountries(principallySpain,Philippines,Morocco,Nigeria,Algeria,France,Sicily,Portugal,Greece,Belgium,Vietnam,Laos,Cambodia,Cyprus,Ghana,Malta,TeraiofNepal,severalregionsofIndia,southwesternChinaandpartsoftheU.S.A.).IncertainpartstheyarefriedassatayasforexampleinBali,wherethisdishisknownassatekakul.