As we saw on the homepage, God has always wanted to relate with Humanity through a Chosen People. He sent his only begotten Son who "pitched his tent amongst us". Before leaving us to take his place at "the right hand of the Father", Jesus promised to send the Spirit to take his place among us.
At Pentecost, the Spirit came in person to guide and empower the Church to bring humanity home to God. Though we have often forgotten him, the Spirit has never left the Church.
The Holy Spirit is a person with a distinct job to do. Like any other person, it is only when we receive the Spirit in a personal way that we can experience a full relationship with him. The Spirit is described as being like a wind, like a fire, like a spring of water pouring out. He is a very dynamic person.
When we receive the Spirit of Pentecost we are:
Purified of our sinfulness like gold purified by fire
Filled with the love of God that is poured into our hearts
Moved by the Spirit like birds souring on the wind
Natural and unstructured meetings with spontaneous praise and intercession, bible readings, personal sharing, hymns etc, allow the Spirit to interact with us more personally and dynamically. Even non-believers can sense something of the Holy Spirit in such gatherings.