http://en.wikipedia.org/wiki/Psalm_100

Waltner, (2006)“Psalm 100 is a simple and beautiful hymn inviting God’s people everywhere to enter into worship with thanksgiving and praise.” Waltner, (2006) found “the whole psalm speaks od joyful response to life, seeking to praise God for all God has done and is.” He wrote “Psalm 100 as a doxology or an expression of praise which concludes the psalm 93, 95-99″ he describes Psalm 100as the psalms of enthronement or kingship, a sort of inauguration.Waltner, J.H.,2006 ‘Believers Church Bible Commentary: Psalms p46-48

Holman Bible Dictionary, (1991) writes,”Hymns lift the congregation’s praise to God, describing God’s greatness and majesty. In the hymn, worshipers invite one another to praise God and to provide reasons for such”. Holman Bible Dictionary, (1991) writes, that psalm 100 is one of these hymns.Fleming, D.M.,1991 Holman Bible Dictionary

Vos, C.J.A.,(2009)”the influence of the psalms as hyms in a liturgical context”, ” Psalm 100 used for Thanksgiving.” Psalm 100 is a hymn which calls for praise by naming the supplicant and giving reason for the praise.” “Psalm 100, the plural imperative of the basic form is used to invite the nations to participate in Israel’s worship(‘enter’ is repeated twice in verses 2 and 4). “The nations are not invited to just any form of worship, but to a festival of worship (‘shout for joy’ is a technical term for festival worship)” “According to psalm 100, knowledge is not a prerequisite for participation in worship, it is gained during acts of worship”Vos, C.J.A., 2009, ‘The Psalms as hymns in a liturgical context’, HTS Teologiese Studies/ Theological Studies 65(1), Art. #105, 6 pages. DOI: 10.4102/hts.v65i1.105