Yoga Sutra 3.2 Unbroken continuation of that mental ability [Dharana] is meditation.

In Dharana, the yogi learns to focus or concentrate on a single object.  Dhyana, meditation, takes the yogi one step further to comprehending or completely understanding the object.  The process is the same as Dharana, concentrating on a single object but in Dharana the intent is to exclude distraction by concentrating where in Dhyana the intent is to understand or comprehend the object through concentration.  Meditation is nothing new to the Christian world though many may not realize it:

63 And Isaac went out to meditate in the field at the eventide: and he lifted up his eyes, and saw, and, behold, the camels were coming.
Genesis 24:63

Clearly, meditation was practiced since the times of the Patriarchs but how similar are biblical meditation and Dhyana?  For this it is best to turn to the Psalms of David:

2 But his delight is in the law of the LORD; and in his law doth he meditate day and night.
Psalms 1:2

1 GIVE ear to my words, O LORD, consider my meditation.
Psalms 5:1

14 Let the words of my mouth, and the meditation of my heart, be acceptable in thy sight, O LORD, my strength, and my redeemer.
Psalms 19:14

6 When I remember thee upon my bed, and meditate on thee in the night watches.
Psalms 63:6

12 I will meditate also of all thy work, and talk of thy doings.
Psalms 77:12

34 My meditation of him shall be sweet: I will be glad in the LORD.
Psalms 104:34

15 I will meditate in thy precepts, and have respect unto thy ways.
Psalms 119:15

97 O how love I thy law! it is my meditation all the day.
98 Thou through thy commandments hast made me wiser than mine enemies: for they are ever with me.
99 I have more understanding than all my teachers: for thy testimonies are my meditation.
100 I understand more than the ancients, because I keep thy precepts.
101 I have refrained my feet from every evil way, that I might keep thy word.
102 I have not departed from thy judgments: for thou hast taught me.
103 How sweet are thy words unto my taste! yea, sweeter than honey to my mouth!
104 Through thy precepts I get understanding: therefore I hate every false way.
Psalms 119:97-104

5 I remember the days of old; I meditate on all thy works; I muse on the work of thy hands.Psalms 143:5

13 Till I come, give attendance to reading, to exhortation, to doctrine.
14 Neglect not the gift that is in thee, which was given thee by prophecy, with the laying on of the hands of the presbytery.
15 Meditate upon these things; give thyself wholly to them; that thy profiting may appear to all.
1 Timothy 4:13-15

David tells us when to meditate (day and night).  That we should make sure our meditation is acceptable to the Lord.  He also tells us on what we should meditate:  The precepts of God, the works of the Lord, the testimonies or scriptures of the Lord and all the doings of the Lord.  Paul adds that we should meditate on the doctrine of God.  The effect of meditation is understanding and wisdom just as Patañjali says we can expect:
Yoga Sutras 3.5 By mastery comes wisdom.

Namasté