According to HeraldScotland, the Marriage and Civil Partnership Bill will legalise civil and religious same-sex marriages, with an "opt-in" procedure for faiths and celebrants willing to conduct ceremonies and legal protection for those who object.
It also relaxes the rules on where civil marriages can take place, and establishes non-religious or "belief" marriage ceremonies.
If approved, the law could take effect by the end of the year, and maybe by July. It depends of the British government. Scotland has indeed to wait the approval of Westminster before being able to regard the law as completely voted. However, Westminster already legalized same-sex marriage in England and in Wales last year, the Scottish marriage equality law will probably be approved very quickly.