They are called Upasarga (Sanskrit: उपसर्ग).
You can refer Wikipedia or Bharat Discovery for simple meanings of Upasargas or prefixed used in Sanskrit/Devanagari.
प्र - अधिक, आगे
प्र - forth, on, onwards, away, forward, very, excessive, great
vi- "apart, asunder"
वि - भिन्न, विशेष
वि - without, apart, away, opposite, intensive, different
So, Vi(वि) used to represent difference or some specialty of the word followed by it.
In the case of Vijnana (विज्ञान), it means some different/special kind of Jnana (ज्ञान) i.e knowledge or intelligence. I recommend to visit this post which clearly defines the Jnana and Vijnana.
Now, talking about Pra (प्र), it usually represents something more/beyond (in the sens of forth) then the meaning of the word followed by it. Like प्रशान्त, प्रख्यात, प्रबल etc. which signifies more than ordinary meanings (of शान्त, ख्यात, बल etc).
In the case of Prajnana (प्रज्ञान), as mentioned above, it enhance/amplifies the ordinary meaning of knowledge, intelligence, wisdom etc. Here, the word Prajnana (प्रज्ञान), Prajna (प्रज्ञा and प्राज्ञ), Jna (ज्ञ) and Jnana (ज्ञान) are closely related. Jna means "knowing" and Prajna means intelligence, wisdom, judgement, understanding, awareness. According to the content, it refers to transcendental wisdom or consciousness.
I recommend to read Aitariya Upanishad 3.1.2 and 3.1.3 for clear understanding of interpreting the Mahavakya.
यदेतद्धृदयं मनश्चैतत् । संज्ञानमाज्ञानं विज्ञानं प्रज्ञानं मेधा दृष्टिर्धृतिमतिर्मनीषा जूतिः स्मृतिः संकल्पः क्रतुरसुः कामो वश इति । सर्वाण्येवैतानि प्रज्ञानस्य नामधेयानि भवंति ॥ २॥
III-i-2: It is this heart (intellect) and this mind that were stated earlier. It is sentience, rulership, secular knowledge, presence of mind, retentiveness, sense-perception, fortitude, thinking, genius, mental suffering, memory, ascertainment resolution, life-activities, hankering, passion and such others. All these verily are the names of Consciousness.
एष ब्रह्मैष इन्द्र एष प्रजापतिरेते सर्वे देवा इमानि च पञ्चमहाभूतानि पृथिवी वायुराकाश आपो ज्योतींषीत्येतानीमानि च क्षुद्रमिश्राणीव । बीजानीतराणि चेतराणि चाण्डजानि च जारुजानि च स्वेदजानि चोद्भिज्जानि चाश्वा गावः पुरुषा हस्तिनो यत्किञ्चेदं प्राणि जङ्गमं च पतत्रि च यच्च स्थावरं सर्वं तत्प्रज्ञानेत्रं प्रज्ञाने प्रतिष्ठितं प्रज्ञानेत्रो लोकः प्रज्ञा प्रतिष्ठा प्रज्ञानं ब्रह्म ॥ ३॥
III-i-3: This One is (the inferior) Brahman; this is Indra, this is Prajapati; this is all these gods; and this is these five elements, viz. earth, air, space, water, fire; and this is all these (big creatures), together with the small ones, that are the procreators of others and referable in pairs - to wit, those that are born of eggs, of wombs, of moisture of the earth, viz. horses, cattle, men, elephants, and all the creatures that there are which move or fly and those which do not move. All these have Consciousness as the giver of their reality; all these are impelled by Consciousness; the universe has Consciousness as its eye and Consciousness is its end. Consciousness is Brahman.
Here Prajnanam refres to Chaitanya (चैतन्य).
Note that Upasarga/Prefix meanings may differ according to the usage in Scripture or sentence.
You should refer Sanskrit grammar or dictionary. Also note though we encourage Sanskrit related questions regarding to interpretation of scripture, you should not ask purely Sanskrit grammar based question. Visit related meta post Should we close questions related to Sanskrit language and grammar as off-topic?. You may follow Sanskrit Languge proosal.