What does it meant that Jesus "breathed on them"? I always tried to visualize the moment when, after Resurrection, Jesus gave Holy Spirit to Apostles:


  So Jesus said to them again, "Peace to you! As the Father has sent
  Me, I also send you." And when He had said this, He breathed on
  them, and said to them, "Receive the Holy Spirit. If you forgive
  the sins of any, they are forgiven them; if you retain the sins of
  any, they are retained." (John 20:21-23, NKJV)


Is the term 'to breath (to give Spirit)' or other to explain how can it be understood? Did Jesus just made a loud voice of a breathe faced towards Apostles? Do people of our times that live in the Spirit make that gestures? In the only moment I recall that gesture (or act of breathing so to speak) with purpose of blessing.

In Genesis we read:


  And the Lord God formed man of the dust of the ground, and breathed
  into his nostrils the breath of life; and man became a living being. (Genesis 2:7, NKJV)


but this can't be really easy to imagine.  

These moments when 'spiritual world' crosses with human, common gestures are so special and make me wonder.
What means that “(Jesus) breathed on them” in John 20,22


  John 20:20-22  And when he had so said, he shewed unto them his hands
  and his side. Then were the disciples glad, when they saw the Lord. 
  Then said Jesus to them again, Peace be unto you: as my Father hath
  sent me, even so send I you.   And when he had said this, he breathed
  on them, and saith unto them, Receive ye the Holy Ghost:


This is the first instance where believers in Jesus receive the indwelling of the Holy Spirit. Those who trusted in God in the Old Testament would occasionally receive the Holy Spirit to prophesy or some other specific task. However, the indwelling Spirit was intended for those who receive their new life in Christ.


  Hebrews 11:39-40  And these all, having obtained a good report through
  faith, received not the promise:   God having provided some better
  thing for us, that they without us should not be made perfect. 
  
  John 5:24  Verily, verily, I say unto you, He that heareth my word,
  and believeth on him that sent me, hath everlasting life, and shall
  not come into condemnation; but is passed from death unto life.


Jesus told his disciples that they would also receive a "baptism" of the Holy Spirit.


  Acts 1:4-5  And, being assembled together with them, commanded them
  that they should not depart from Jerusalem, but wait for the promise
  of the Father, which, saith he, ye have heard of me.   For John truly
  baptized with water; but ye shall be baptized with the Holy Ghost not
  many days hence.


This was an additional dispensation of the Holy Spirit that was prophesied by Joel and was to be a sign as well as a means of establishing the Kingdom.


  Acts 2:16-17  But this is that which was spoken by the prophet Joel;
  And it shall come to pass in the last days, saith God, I will pour out
  of my Spirit upon all flesh: and your sons and your daughters shall
  prophesy, and your young men shall see visions, and your old men shall
  dream dreams:


The idea that the Holy Spirit was given in two steps is not accepted by everyone. However I think we can see that the Holy Spirit was given a second time by the laying on of hands of those who had already professed their faith and been baptized constitutes a second reception of the Holy Spirit.


  Acts 8:14-17  Now when the apostles which were at Jerusalem heard that
  Samaria had received the word of God, they sent unto them Peter and
  John:   Who, when they were come down, prayed for them, that they
  might receive the Holy Ghost:   (For as yet he was fallen upon none of
  them: only they were baptized in the name of the Lord Jesus.)   Then
  laid they their hands on them, and they received the Holy Ghost.


As I understand the Bible, the second reception of the Holy Spirit was consistent with the immanency of the Kingdom of God. Since Israel was not even provoked by jealousy, and did not receive this kingdom offer, today we are left with just the indwelling Holy Spirit as proof of our new life in Jesus.


  2 Corinthians 1:21-22  Now he which stablisheth us with you in Christ,
  and hath anointed us, is God;   Who hath also sealed us, and given the
  earnest of the Spirit in our hearts.


When a faithful remnant of Israel does finally receive the kingdom, we shall once again see the reception of the Holy Spirit through the laying on of hands resume.