Different behavior at home and outside.

My baby behave very differently at home and outside. She is aCtive and loud when at home. And cries more too. However, She is very quiet and well behave when friends and relatives came to visit. Going outside also, she will clench her fist and stay very still when being carried or in stroller. Ha ha... seems so nervous when seeing unfamiliar things. Jus curious, any mummies also observe this behavior.. please share. =)